Use of aspherical colloidal silica particles as abrasive grains of a polishing composition mainly for a purpose of improving a polishing rate is conventionally known. For example, Japanese Laid-Open Patent Publication No. 2007-153732 (Patent Document 1) discloses use of colloidal silica particles having numerous small protrusions on the surfaces thereof for mirror polishing of a silicon wafer. Also, Japanese Laid-Open Patent Publication No. 2009-149493 (Patent Document 2) discloses a polishing composition using, as abrasive grains, silica sol in which silica particles having a minor diameter/major diameter ratio in a range of 0.01 to 0.8 and having a plurality of wart-like protrusions on the surfaces thereof are contained.
However, there is still present a demand for a polishing composition containing colloidal silica particles that enables the realization of a higher polishing rate.